The dental filter currently used in dental offices is a simple plastic perforated screen which is located in the vacuum conduit line leading to the sewer line. This filter fails to accomplish all needed functions of a dental filter.
The dentist and dental assistant sit on adjustable stools on opposite sides of the reclined contour dental chair near the patient's head. The dentist prepares the patient's teeth for restoration with a high speed turbine handpiece (drill) to remove decay and shape the tooth to be restored. During some parts of the procedure a water spray is used to wash the tooth and the operating field (washed field technique). Tooth structure particles and/or existing old defective silver-mercury amalgam or gold restorations are aspirated from the operating field of the oral cavity. This aspiration is done by the dental assistant using a vacuum tip attached to a conventional flexible vacuum tubing. The solids, water spray and oral fluids are deposited via the vacuum tubing into the perforated plastic screen and from there are deposited into the sewer line.
The dental filter currently in use suffers from many disadvantages and fails completely to accomplish the function of a dental filter:
(a) The particles of the silver-mercury amalgam, gold and tooth structure produced by the drilling procedure are reduced to a very small particle size. These small particles escape through the perforations of the plastic screen and are lost into the sewer system. PA1 (b) Mercury, also a heavy metal, is a liquid at room temperature and in its free state is a very toxic substance. Therefore, if liquid mercury is accidentally spilled on operating surfaces or on the floor, it can be easily aspirated up by the vacuum tip. However, it easily escapes through the plastic screen perforations. The mercury then enters the sewer lines and ultimately into the environment. PA1 (c) Another defective feature in the above described filter screen is that the aspirated water and oral fluids are aspirated together along with the solid materials being removed from the oral cavity. PA1 (d) The perforated screen type filter does not allow for the separation of the water fluid phase from the solids phase during the dental procedure.